Field of the Invention
The present invention relates to a power transmission apparatus, a power reception apparatus, a wireless power feeding system, a control method.
Description of the Related Art
The following four methods are used for supplying power in a non-contact manner (wirelessly): an electromagnetic induction method, a magnetic resonance method, an electric field coupling method, and a radio wave reception method. In recent years, among these four methods, the magnetic resonance method has drawn attention. With this method, sufficient power can be transmitted and a long power transmission distance can be ensured. For example, as such magnetic resonance method, by utilizing this power transmission distance, Japanese Patent Application Laid-Open No. 2009-136132 discusses a 1-to-N power feeding method for allowing a power transmission apparatus to transmit power to a plurality of wireless power reception apparatuses.
According to Japanese Patent Application Laid-Open No. 2009-136132, in a standby mode in which the power transmission apparatus is not feeding power, the power transmission apparatus transmits certain pulse signals to determine whether any wireless power reception apparatus has come close within a few meters of the power transmission apparatus. If a wireless power reception apparatus transmits its own unique identification data (ID) to the power transmission apparatus, the power transmission apparatus determines whether this wireless power reception apparatus is a wireless power reception apparatus as a target for power feeding. If the wireless power reception apparatus is determined to be a target, the power transmission apparatus feeds power to the wireless power reception apparatus. In this operation, the power transmission apparatus can transmit unique codes to the wireless power reception apparatus so that the wireless power reception apparatus can receive respective data such as a charge amount and a device status from the power transmission apparatus.
However, different power reception apparatuses have different specifications. For example, as discussed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-513563, a plasma display panel (PDP) requires accurate voltage levels from a power feeding device for addressing and sustain voltages used for display. To adjust an output voltage from the power feeding device, a load device, a control signal setting unit, and a control unit are added to a device for performing power feeding. The load device has the control signal setting unit for outputting a control signal in response to an output parameter value supplied from the power feeding device. The power feeding device has a control unit for receiving the control signal. The power feeding device controls the output voltage by performing feedback through these added units and devices.